The present invention relates to a method of controlling a composite intake manifold system for use with an internal combustion engine, capable of varying the effective length of intake pipes dependent on the rotational speed of the engine for thereby obtaining an appropriate intake air inertial effect in various engine speed ranges from low to high speed ranges.
There is known an intake manifold system of a variable intake pipe length for use with an internal combustion engine, as disclosed in Japanese Laid-Open Patent Publication No. 61(1986)-4823 corresponding to U.S. Pat. No. 4,664,076. According to the disclosed intake manifold system, the inertial effect of intake air can be adjusted or controlled depenent on the rotational speed of the engine. More specifically, the intake manifold system includes longer intake passages and shorter intake passages having bypass valves therein. As the engine speed increases, the bypass valves in the shorter intake passages are progressively opened to reduce the effective length of intake pipes.
The above bypass valves are controlled by a complex and expensive mechanism comprising a diaphragm actuator controlled by solenoid-operated valves and a step motor. It has not been easy to control the opening of the bypass valves to achieve a high-torque opening setting at all times throughout various engine speed ranges